chore: remove obsolete AGENTS.md, build.sh, and misplaced package-lock.json (#1463)

- Remove AGENTS.md (superseded by CLAUDE.md and .cursor/rules)
- Remove build.sh script (broken import paths, unused since 2021)
- Remove orphaned package-lock.json from root (belongs in website/)
- Add golden snapshot warning to CLAUDE.md from AGENTS.md

These files were creating confusion and the package-lock.json in root
was orphaned without a corresponding package.json file.

Co-authored-by: Andriy Knysh <[email protected]>

Author: osterman

AGENTS.md

@@ -293,6 +293,12 @@ Use fixtures in `tests/test-cases/` for integration tests. Each test case should
 - `stacks/` - Stack definitions
 - `components/` - Component configurations
 
+### Golden Snapshots (MANDATORY)
+- **NEVER modify files under `tests/test-cases/` or `tests/testdata/`** unless explicitly instructed
+- These directories contain golden snapshots that are sensitive to even minor changes
+- Golden snapshots are used to verify expected output remains consistent
+- If you need to update golden snapshots, do so intentionally and document the reason
+
 ## Common Development Tasks
 
 ### Adding New CLI Command